falsecolor: The LUT file name property is not displayed on the property dialog from dock

**Describe the bug**

`OBS_PROPERTY_PATH` is not implemented in the property dialog for the dock. This results in the property is not displayed on the property dialog.

**Expected behavior**
The property "LUT file name" should appear on the property for the false color on the dock.

**Actual behavior**
The property does not appear.

**Additional context**
The property was added by #87.